CHANGES IN KNEE KINEMATICS AFTER APPLICATION OF AN ARTICULATED EXTERNAL FIXATOR IN NORMAL AND POSTERIOR CRUCIATE LIGAMENT-DEFICIENT KNEES

We studied how the location of an articulated external fixator, the EB I-Orthofix (EBI Corp, Persippany, NJ), affects the kinematics of the p osterior cruciate ligament (PCL)-deficient knee. Ten unembalmed cadave r whole lower limbs were randomly divided into two groups of five Limb s each: (1) fixator hinge located near the average knee flexion axis ( the anatomic position group); and (2) fixator hinge located distal to the joint line and posterior to the flexion axis (the fibular styloid position group). Three loading conditions, passive flexion/extension, flexion/extension with anterior force of 100 N, and flexion/extension with posterior force of 100 N were used for each knee with the PCL int act and with the PCL cut. With the fixator located in the anatomic pos ition, and after cutting of the PCL, posterior translation was reduced to normal limits only at flexion angles less than or equal to 15 degr ees. In this configuration, the fixator was ineffective at minimizing posterior translation at flexion angles greater than or equal to 30 de grees. With the fixator located at the fibular styloid position, howev er, posterior translation of the tibia in the PCL deficient knees was reduced to near normal limits at all flexion angles. These results wer e statistically different than the anatomic position group at all flex ion angles greater than or equal to 30 degrees (P < .01). The external fixator appears to allow normal range of motion while effectively shi elding the PCL graft from stress caused by posterior translational for ces. Issues related to the potential complications and patient accepta nce must be addressed thoroughly before this technique is applied in c linical practice.